Conventionally tubes have a constant cross section over their entire length. From the prior art e.g. glass tubes having a circular cross section are known for use as packaging containers for pharmaceutical substances, for use in lighting or for applications in solar heating. Oval glass tubes having a non-circular cross section are distributed by the applicant under the trademarks Conturax® und Conturax Pro®. Their profile is constant over the entire length of the glass tubes. Oval tabes are also used for fluorescent lamps (see JP 61224257 A2).
Tubes of plastic material or of a plastic composite material having a non-circular cross section are used e.g. in floor heating systems.
DE 545 449 A discloses an apparatus for deforming or shaping glass tubes to glass tubes having a non-circular profile, wherein the glass tubes are conveyed through a nip in a heated state. DE 1007962 A discloses a corresponding method for shaping glass tubes to thin insulating tapes or insulating layers. DE 102006015223 B3 of the Applicant discloses a method and an apparatus for producing a glass tube having a profile that differs from a circular profile. Here, the initial glass tube having the initial profile (so-called preform) first passes through a hot zone while forming a drawing bulb and then passes a nip formed by a pair of rollers, where the drawing bulb is shaped (deformed) to a glass tube having a different profile. All of the afore-mentioned glass tubes have a constant profile over their entire length.
JP 2006315919 A und JP 2006004660 A2 disclose glass tubes for cold-cathode fluorescent lamps (CCFL) having sections that have a non-circular cross section, that alternate with sections that have a circular cross section. For this purpose, a glass tube is deformed, in sections, in a hot malleable state and is partially also bent. The glass tubes are molten off at the ends, but are not open at their ends and thus cannot be connected with connecting members or adjacent glass tubes.